Load Testing of Instrumented Pavement Sections

This report summarizes and references seven previously written reports developed from this project. The objective of this project was to use the field-measured strains from a number of MnROAD cells to develop mechanistically based load equivalency factors (LEF). The load equivalency factors commonly in use were developed from the AASHTO Road Test conducted in the late 1950s at Ottawa, Illinois. The AASHTO-based LEF represented the pavement behavior at the Road Test and might not reflect conditions in other climates, other subgrade soils, pavement sections, traffic and so on. Several of the MnROAD project objectives related to the development of improved mechanistic models and the development of improved pavement design methods. The Load Testing of Instrumented Pavement Sections project included strain measurements from a variety of vehicle loads, including single, tandem, and tridem axles, tire pressures, tire types, various vehicle speeds, and several different seasons. The testing and analysis resulted in the evaluation of various mechanistic models and the selection of WESLEA for flexible pavements and ISLAB2000 for rigid pavements. Many of the strain sensors, installed during construction in 1993 or 1994, no longer worked limiting the number of test cells available and the scope of the study. The LEF analysis for flexible pavements were based on only the tensile strain at the bottom of the asphalt, and were generally lower than the corresponding AASHTO factors. There were too few strain sensors available to conduct an LEF analysis on rigid pavements, however, during the selection of ISLAB2000, a number of relationships were developed that relate k-value, to other factors such as slab thickness, slab elastic modulus, and strain.